Field
Embodiments of the present invention relate to a light source device and a projector having the light source device.
Description of the Related Art
In recent years, time-sharing type projectors have become popular, in which, light of a plurality of wavelengths is extracted in a time sharing manner, and the extracted light of a plurality of wavelengths is successively modulated to form and project an image. With such a light source device, light such as a white light emitted from the light source is allowed to incident on the rotating wheel that is spinning at a constant speed, and light of a plurality of wavelengths (e.g., a blue light, a green light, a red light) can be extracted in a time sharing manner.
Also, there has been proposed a light source device, that includes a light source such as a semiconductor laser configured to emit light of a single wavelength, and a rotating wheel in which fluorescent layers are arranged in place of color filters, and light of a single wavelength emitted from a light source such as a semiconductor laser is allowed to incident on the rotating wheel so that light of a plurality of wavelengths is extracted in a time sharing manner. For example, blue light emitted from a semiconductor laser can be converted by the phosphor into green light or red light.
One example of such a device is proposed in JP 2011-133782A where in order to obtain a uniform luminance at the time of projecting light, a plurality of laser light sources each emits light of substantially elliptical cross-section are arranged so that major axes directions of the elliptical cross-sections of the laser light sources are changed sequentially to widen the projecting area when light emitted from a plurality of laser light sources are condensed on the phosphor layer.
Also, in a device proposed in JP 2012-215633A, a plurality of laser light sources are arranged at an interval with each other and the collimator lenses disposed at emission surface side and corresponding to respective laser light sources are arranged with shifted distances so that light of the laser light sources are condensed on different points on the phosphor layer, so that the light density can be decreased when exciting the phosphor.
Also, in a device proposed in JP 2012-159603A, a diffraction optical element is disposed between a laser light source and a phosphor wheel so that the laser beams can be condensed on a plurality of points on the phosphor layer, and thus the light density can be decreased when exciting the phosphor.
As in the light source device shown in JP 2011-133782A, in the case where a plurality of laser light sources each emits light of substantially elliptical cross-section are arranged so that major axes directions of the elliptical cross-sections of the laser light sources are changed sequentially, the major axes directions of the laser light sources are needed to be adjusted, respectively. In addition, the laser beams are condensed on a same location, resulting in a high light density in the center portion and a decrease in the luminous efficiency of the phosphor.
In the case of the light source device shown in JP 2012-215633A, light of the laser light sources are condensed on different points that allows for a change of the condensed point, but a parallel light emitted from the collimating lens has a high light density due to its small condensing diameter, which may result in a decrease in the luminous efficiency. Moreover, in the light source devices shown in JP 2011-133782A and JP 2012-215633A, the beam shape at the condensed region of the condensing lens depends on the far field pattern or the near field pattern of the semiconductor laser, so that a beam shape of desired size and/or a beam shape of desired aspect ratio is difficult to obtain.
In the case of the light source device shown in JP-2012-159603A, the use of the diffraction optical element requires a high cost.